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Queen's Challenge

This is a port of an older Flash game that I created. The goal of this puzzle is to place 8 Queens on a chess board in such a way that none of the Queens can capture another Queen. For those of you who, like me, are not chess players, the Queen is able to move any number of spaces but only horizontally, vertically, or diagonally with diagonally being 45, 135, 225, 315 degrees. To make things more challenging, the first queen is placed for you, so knowing a winning solution will only help you out in only one of every eight games. Simply click on the tiles where you want to place your Queens and if there are no conflicts than a Queen will be placed on the board at that location. If you are using a mouse, there will be highlights showing you what tiles are valid.

If you are having trouble solving this puzzle, or curious about how computer's solve puzzles, there is a solve menu on the right. Brute Force is just the machine trying all the moves, which as you can see would take a really long time. By taking advantage of the fact that we know there can only be a single queen per line, brute lines is a bit better but is still going to take a really long time to solve the puzzle. Backtracking drastically improves the search speed by detecting when a layout is not going to work and skipping the remaining moves in that layout. Finally, forward checking adds the ability to look at the possible moves to detect when a potential move will be problematic for a later queen.